Anti-tumor potential of temperature-sensitive p53 mutants

The p53 tumor suppressor is frequently inactivated by mutations in cancer. Most p53 point mutations are located in the DNA binding domain that prevent folding or disrupt the DNA binding surface. Rescuing the structural defect and transcriptional activity of mutant p53 in tumor cells should induce cell death or cell cycle arrest that bring significant therapeutic benefits. However, this hypothesis remains unproven because currently there are no specific drugs capable of efficiently reactivating mutant p53. To bypass this limitation and rigorously test the clinical potential of mutant p53 functional rescue, we established a procedure to induce sustained hypothermia in mice by pharmacological blockade of brain- regulated thermogenesis. This mouse model enabled us to use hypothermia to reactivate temperature- sensitive (ts) p53 mutants in tumors to evaluate therapeutic efficacy. Preliminary experiments demonstrated the ability of ts p53 activation in combination with chemotherapy to induce regression of lymphoma xenografts. Importantly, durable remission was observed in a subset of tumors. This promising finding provides proof-of-concept for mutant p53 functional rescue as a potential cancer treatment. Furthermore, since ~14% of p53 point mutants in cancer are temperature-sensitive, our results raised the possibility of using therapeutic hypothermia to treat tumors expressing ts mutant p53. To explore the translational potential and molecular mechanism of this novel approach, we propose the following specific aims: (1) Investigate tumor response to ts p53 activation and optimize therapeutic efficacy. (2) Investigate the potential of ts mutant p53 in solid tumors and PDX models. (3) Investigate the effect of endogenous ts p53 activation using a genetically engineered mouse model. (4) Identify all p53 ts mutants with tumor suppressor activity in vivo by saturation screen. These experiments will provide proof-of-concept for specific targeting of tumors expressing ts mutant p53, with the potential to impact a large number of cancer patients.